Adding upstream version 115.7.0esr.upstream/115.7.0esrupstream

Signed-off-by: Daniel Baumann <daniel.baumann@progress-linux.org>

1 files changed, 786 insertions, 0 deletions

diff --git a/build/moz.configure/rust.configure b/build/moz.configure/rust.configure
new file mode 100644
index 0000000000..7a2fd1ae70
--- /dev/null
+++ b/build/moz.configure/rust.configure
@@ -0,0 +1,786 @@
+# -*- Mode: python; indent-tabs-mode: nil; tab-width: 40 -*-
+# vim: set filetype=python:
+# This Source Code Form is subject to the terms of the Mozilla Public
+# License, v. 2.0. If a copy of the MPL was not distributed with this
+# file, You can obtain one at http://mozilla.org/MPL/2.0/.
+
+
+# Rust is required by `rust_compiler` below. We allow_missing here
+# to propagate failures to the better error message there.
+option(env="RUSTC", nargs=1, help="Path to the rust compiler")
+option(env="CARGO", nargs=1, help="Path to the Cargo package manager")
+
+rustc = check_prog(
+    "_RUSTC",
+    ["rustc"],
+    what="rustc",
+    paths=rust_search_path,
+    input="RUSTC",
+    allow_missing=True,
+)
+cargo = check_prog(
+    "_CARGO",
+    ["cargo"],
+    what="cargo",
+    paths=rust_search_path,
+    input="CARGO",
+    allow_missing=True,
+)
+
+
+@template
+def unwrap_rustup(prog, name):
+    # rustc and cargo can either be rustup wrappers, or they can be the actual,
+    # plain executables. For cargo, on OSX, rustup sets DYLD_LIBRARY_PATH (at
+    # least until https://github.com/rust-lang/rustup.rs/pull/1752 is merged
+    # and shipped) and that can wreak havoc (see bug 1536486). Similarly, for
+    # rustc, rustup silently honors toolchain overrides set by vendored crates
+    # (see bug 1547196).
+    #
+    # In either case, we need to find the plain executables.
+    #
+    # To achieve that, try to run `PROG +stable`. When the rustup wrapper is in
+    # use, it either prints PROG's help and exits with status 0, or prints
+    # an error message (error: toolchain 'stable' is not installed) and exits
+    # with status 1. In the cargo case, when plain cargo is in use, it exits
+    # with a different error message (e.g. "error: no such subcommand:
+    # `+stable`"), and exits with status 101.
+    #
+    # Unfortunately, in the rustc case, when plain rustc is in use,
+    # `rustc +stable` will exit with status 1, complaining about a missing
+    # "+stable" file. We'll examine the error output to try and distinguish
+    # between failing rustup and failing rustc.
+    @depends(prog, dependable(name))
+    @imports(_from="__builtin__", _import="open")
+    @imports("os")
+    def unwrap(prog, name):
+        if not prog:
+            return
+
+        def from_rustup_which():
+            out = check_cmd_output("rustup", "which", name, executable=prog).rstrip()
+            # If for some reason the above failed to return something, keep the
+            # PROG we found originally.
+            if out:
+                log.info("Actually using '%s'", out)
+                return out
+
+            log.info("No `rustup which` output, using '%s'", prog)
+            return prog
+
+        (retcode, stdout, stderr) = get_cmd_output(prog, "+stable")
+
+        if name == "cargo" and retcode != 101:
+            prog = from_rustup_which()
+        elif name == "rustc":
+            if retcode == 0:
+                prog = from_rustup_which()
+            elif "+stable" in stderr:
+                # PROG looks like plain `rustc`.
+                pass
+            else:
+                # Assume PROG looks like `rustup`. This case is a little weird,
+                # insofar as the user doesn't have the "stable" toolchain
+                # installed, but go ahead and unwrap anyway: the user might
+                # have only certain versions, beta, or nightly installed, and
+                # we'll catch invalid versions later.
+                prog = from_rustup_which()
+
+        return normalize_path(prog)
+
+    return unwrap
+
+
+rustc = unwrap_rustup(rustc, "rustc")
+cargo = unwrap_rustup(cargo, "cargo")
+
+
+set_config("CARGO", cargo)
+set_config("RUSTC", rustc)
+
+
+@depends_if(rustc)
+@checking("rustc version", lambda info: info.version)
+def rustc_info(rustc):
+    if not rustc:
+        return
+    out = check_cmd_output(rustc, "--version", "--verbose").splitlines()
+    info = dict((s.strip() for s in line.split(":", 1)) for line in out[1:])
+    return namespace(
+        version=Version(info.get("release", "0")),
+        commit=info.get("commit-hash", "unknown"),
+        host=info["host"],
+        llvm_version=Version(info.get("LLVM version", "0")),
+    )
+
+
+set_config(
+    "RUSTC_VERSION",
+    depends(rustc_info)(lambda info: str(info.version) if info else None),
+)
+
+
+set_config(
+    "RUSTC_LLVM_VERSION",
+    depends(rustc_info)(lambda info: str(info.llvm_version) if info else None),
+)
+
+set_config(
+    "MOZ_CLANG_NEWER_THAN_RUSTC_LLVM",
+    depends(c_compiler, rustc_info)(
+        lambda c_compiler, rustc_info: rustc_info
+        and c_compiler.type == "clang"
+        and c_compiler.version.major > rustc_info.llvm_version.major
+    ),
+)
+
+
+@depends_if(cargo)
+@checking("cargo version", lambda info: info.version)
+@imports("re")
+def cargo_info(cargo):
+    if not cargo:
+        return
+    out = check_cmd_output(cargo, "--version", "--verbose").splitlines()
+    info = dict((s.strip() for s in line.split(":", 1)) for line in out[1:])
+    version = info.get("release")
+    # Older versions of cargo didn't support --verbose, in which case, they
+    # only output a not-really-pleasant-to-parse output. Fortunately, they
+    # don't error out, so we can just try some regexp matching on the output
+    # we already got.
+    if version is None:
+        VERSION_FORMAT = r"^cargo (\d\.\d+\.\d+).*"
+
+        m = re.search(VERSION_FORMAT, out[0])
+        # Fail fast if cargo changes its output on us.
+        if not m:
+            die("Could not determine cargo version from output: %s", out)
+        version = m.group(1)
+
+    return namespace(
+        version=Version(version),
+    )
+
+
+@depends(rustc_info, cargo_info, target)
+@imports(_from="mozboot.util", _import="MINIMUM_RUST_VERSION")
+@imports(_from="textwrap", _import="dedent")
+def rust_compiler(rustc_info, cargo_info, target):
+    if not rustc_info:
+        die(
+            dedent(
+                """\
+        Rust compiler not found.
+        To compile rust language sources, you must have 'rustc' in your path.
+        See https://www.rust-lang.org/ for more information.
+
+        You can install rust by running './mach bootstrap'
+        or by directly running the installer from https://rustup.rs/
+        """
+            )
+        )
+    rustc_min_version = Version(MINIMUM_RUST_VERSION)
+    cargo_min_version = rustc_min_version
+
+    version = rustc_info.version
+    is_nightly = "nightly" in version.version
+    is_version_number_match = (
+        version.major == rustc_min_version.major
+        and version.minor == rustc_min_version.minor
+        and version.patch == rustc_min_version.patch
+    )
+
+    if version < rustc_min_version or (is_version_number_match and is_nightly):
+        die(
+            dedent(
+                """\
+        Rust compiler {} is too old.
+
+        To compile Rust language sources please install at least
+        version {} of the 'rustc' toolchain (or, if using nightly,
+        at least one version newer than {}) and make sure it is
+        first in your path.
+
+        You can verify this by typing 'rustc --version'.
+
+        If you have the 'rustup' tool installed you can upgrade
+        to the latest release by typing 'rustup update'. The
+        installer is available from https://rustup.rs/
+        """.format(
+                    version, rustc_min_version, rustc_min_version
+                )
+            )
+        )
+
+    if target.kernel == "WINNT" and (version.major, version.minor) == (1, 56):
+        die(
+            dedent(
+                """\
+        Rust compiler 1.56.* is not supported for Windows builds.
+
+        Use a newer or an older version.
+
+        See https://github.com/rust-lang/rust/issues/88576.
+        """
+            )
+        )
+
+    if not cargo_info:
+        die(
+            dedent(
+                """\
+        Cargo package manager not found.
+        To compile Rust language sources, you must have 'cargo' in your path.
+        See https://www.rust-lang.org/ for more information.
+
+        You can install cargo by running './mach bootstrap'
+        or by directly running the installer from https://rustup.rs/
+        """
+            )
+        )
+
+    version = cargo_info.version
+    if version < cargo_min_version:
+        die(
+            dedent(
+                """\
+        Cargo package manager {} is too old.
+
+        To compile Rust language sources please install at least
+        version {} of 'cargo' and make sure it is first in your path.
+
+        You can verify this by typing 'cargo --version'.
+        """
+            ).format(version, cargo_min_version)
+        )
+
+    return True
+
+
+@depends(rustc, when=rust_compiler)
+@imports(_from="__builtin__", _import="ValueError")
+def rust_supported_targets(rustc):
+    out = check_cmd_output(rustc, "--print", "target-list").splitlines()
+    data = {}
+    for t in out:
+        try:
+            info = split_triplet(t, allow_wasi=True)
+        except ValueError:
+            if t.startswith("thumb"):
+                cpu, rest = t.split("-", 1)
+                retry = "-".join(("arm", rest))
+            else:
+                continue
+            try:
+                info = split_triplet(retry, allow_wasi=True)
+            except ValueError:
+                continue
+        key = (info.cpu, info.endianness, info.os)
+        data.setdefault(key, []).append(namespace(rust_target=t, target=info))
+    return data
+
+
+def detect_rustc_target(
+    host_or_target, compiler_info, arm_target, rust_supported_targets
+):
+    # Rust's --target options are similar to, but not exactly the same
+    # as, the autoconf-derived targets we use.  An example would be that
+    # Rust uses distinct target triples for targetting the GNU C++ ABI
+    # and the MSVC C++ ABI on Win32, whereas autoconf has a single
+    # triple and relies on the user to ensure that everything is
+    # compiled for the appropriate ABI.  We need to perform appropriate
+    # munging to get the correct option to rustc.
+    # We correlate the autoconf-derived targets with the list of targets
+    # rustc gives us with --print target-list.
+    candidates = rust_supported_targets.get(
+        (host_or_target.cpu, host_or_target.endianness, host_or_target.os), []
+    )
+
+    def find_candidate(candidates):
+        if len(candidates) == 1:
+            return candidates[0].rust_target
+        elif not candidates:
+            return None
+
+        # We have multiple candidates. There are two cases where we can try to
+        # narrow further down using extra information from the build system.
+        # - For windows targets, correlate with the C compiler type
+        if host_or_target.kernel == "WINNT":
+            if host_or_target.abi:
+                if host_or_target.abi == "msvc":
+                    suffix = "windows-msvc"
+                elif host_or_target.abi == "mingw":
+                    suffix = "windows-gnu"
+            elif compiler_info.type in ("gcc", "clang"):
+                suffix = "windows-gnu"
+            else:
+                suffix = "windows-msvc"
+            narrowed = [
+                c for c in candidates if c.rust_target.endswith("-{}".format(suffix))
+            ]
+            if len(narrowed) == 1:
+                return narrowed[0].rust_target
+            elif narrowed:
+                candidates = narrowed
+
+            vendor_aliases = {"pc": ("w64", "windows")}
+            narrowed = [
+                c
+                for c in candidates
+                if host_or_target.vendor in vendor_aliases.get(c.target.vendor, ())
+            ]
+
+            if len(narrowed) == 1:
+                return narrowed[0].rust_target
+
+        # - For arm targets, correlate with arm_target
+        #   we could be more thorough with the supported rust targets, but they
+        #   don't support OSes that are supported to build Gecko anyways.
+        #   Also, sadly, the only interface to check the rust target cpu features
+        #   is --print target-spec-json, and it's unstable, so we have to rely on
+        #   our own knowledge of what each arm target means.
+        if host_or_target.cpu == "arm" and host_or_target.endianness == "little":
+            prefixes = []
+            if arm_target.arm_arch >= 7:
+                if arm_target.thumb2 and arm_target.fpu == "neon":
+                    prefixes.append("thumbv7neon")
+                if arm_target.thumb2:
+                    prefixes.append("thumbv7a")
+                prefixes.append("armv7")
+            if arm_target.arm_arch >= 6:
+                prefixes.append("armv6")
+                if host_or_target.os != "Android":
+                    # arm-* rust targets are armv6... except arm-linux-androideabi
+                    prefixes.append("arm")
+            if arm_target.arm_arch >= 5:
+                prefixes.append("armv5te")
+                if host_or_target.os == "Android":
+                    # arm-* rust targets are armv6... except arm-linux-androideabi
+                    prefixes.append("arm")
+            if arm_target.arm_arch >= 4:
+                prefixes.append("armv4t")
+            # rust freebsd targets are the only ones that don't have a 'hf' suffix
+            # for hard-float. Technically, that means if the float abi ever is not
+            # hard-float, this will pick a wrong target, but since rust only
+            # supports hard-float, let's assume that means freebsd only support
+            # hard-float.
+            if arm_target.float_abi == "hard" and host_or_target.os != "FreeBSD":
+                suffix = "hf"
+            else:
+                suffix = ""
+            for p in prefixes:
+                for c in candidates:
+                    if c.rust_target.startswith(
+                        "{}-".format(p)
+                    ) and c.rust_target.endswith(suffix):
+                        return c.rust_target
+
+        # See if we can narrow down on the exact alias.
+        # We use the sub_configure_alias to keep support mingw32 triplets as input.
+        narrowed = [
+            c
+            for c in candidates
+            if c.target.sub_configure_alias == host_or_target.sub_configure_alias
+        ]
+        if len(narrowed) == 1:
+            return narrowed[0].rust_target
+        elif narrowed:
+            candidates = narrowed
+
+        # See if we can narrow down with the raw OS
+        narrowed = [c for c in candidates if c.target.raw_os == host_or_target.raw_os]
+        if len(narrowed) == 1:
+            return narrowed[0].rust_target
+        elif narrowed:
+            candidates = narrowed
+
+        # See if we can narrow down with the raw OS and raw CPU
+        narrowed = [
+            c
+            for c in candidates
+            if c.target.raw_os == host_or_target.raw_os
+            and c.target.raw_cpu == host_or_target.raw_cpu
+        ]
+        if len(narrowed) == 1:
+            return narrowed[0].rust_target
+
+        # Finally, see if the vendor can be used to disambiguate.
+        narrowed = [c for c in candidates if c.target.vendor == host_or_target.vendor]
+        if len(narrowed) == 1:
+            return narrowed[0].rust_target
+
+        return None
+
+    rustc_target = find_candidate(candidates)
+
+    if rustc_target is None:
+        die("Don't know how to translate {} for rustc".format(host_or_target.alias))
+
+    return rustc_target
+
+
+@imports("os")
+@imports(_from="tempfile", _import="mkstemp")
+@imports(_from="textwrap", _import="dedent")
+@imports(_from="mozbuild.configure.util", _import="LineIO")
+def assert_rust_compile(host_or_target, rustc_target, rustc):
+    # Check to see whether our rustc has a reasonably functional stdlib
+    # for our chosen target.
+    target_arg = "--target=" + rustc_target
+    in_fd, in_path = mkstemp(prefix="conftest", suffix=".rs", text=True)
+    out_fd, out_path = mkstemp(prefix="conftest", suffix=".rlib")
+    os.close(out_fd)
+    try:
+        source = b'pub extern fn hello() { println!("Hello world"); }'
+        log.debug("Creating `%s` with content:", in_path)
+        with LineIO(lambda l: log.debug("| %s", l)) as out:
+            out.write(source)
+
+        os.write(in_fd, source)
+        os.close(in_fd)
+
+        cmd = [
+            rustc,
+            "--crate-type",
+            "staticlib",
+            target_arg,
+            "-o",
+            out_path,
+            in_path,
+        ]
+
+        def failed():
+            die(
+                dedent(
+                    """\
+            Cannot compile for {} with {}
+            The target may be unsupported, or you may not have
+            a rust std library for that target installed. Try:
+
+              rustup target add {}
+            """.format(
+                        host_or_target.alias, rustc, rustc_target
+                    )
+                )
+            )
+
+        check_cmd_output(*cmd, onerror=failed)
+        if not os.path.exists(out_path) or os.path.getsize(out_path) == 0:
+            failed()
+    finally:
+        os.remove(in_path)
+        os.remove(out_path)
+
+
+@depends(
+    rustc,
+    host,
+    host_c_compiler,
+    rustc_info.host,
+    rust_supported_targets,
+    arm_target,
+    when=rust_compiler,
+)
+@checking("for rust host triplet")
+@imports(_from="textwrap", _import="dedent")
+def rust_host_triple(
+    rustc, host, compiler_info, rustc_host, rust_supported_targets, arm_target
+):
+    rustc_target = detect_rustc_target(
+        host, compiler_info, arm_target, rust_supported_targets
+    )
+    if rustc_target != rustc_host:
+        if host.alias == rustc_target:
+            configure_host = host.alias
+        else:
+            configure_host = "{}/{}".format(host.alias, rustc_target)
+        die(
+            dedent(
+                """\
+        The rust compiler host ({rustc}) is not suitable for the configure host ({configure}).
+
+        You can solve this by:
+        * Set your configure host to match the rust compiler host by editing your
+        mozconfig and adding "ac_add_options --host={rustc}".
+        * Or, install the rust toolchain for {configure}, if supported, by running
+        "rustup default stable-{rustc_target}"
+        """.format(
+                    rustc=rustc_host,
+                    configure=configure_host,
+                    rustc_target=rustc_target,
+                )
+            )
+        )
+    assert_rust_compile(host, rustc_target, rustc)
+    return rustc_target
+
+
+@depends(
+    rustc, target, c_compiler, rust_supported_targets, arm_target, when=rust_compiler
+)
+@checking("for rust target triplet")
+def rust_target_triple(
+    rustc, target, compiler_info, rust_supported_targets, arm_target
+):
+    rustc_target = detect_rustc_target(
+        target, compiler_info, arm_target, rust_supported_targets
+    )
+    assert_rust_compile(target, rustc_target, rustc)
+    return rustc_target
+
+
+set_config("RUST_TARGET", rust_target_triple)
+set_config("RUST_HOST_TARGET", rust_host_triple)
+
+
+# This is used for putting source info into symbol files.
+set_config("RUSTC_COMMIT", depends(rustc_info)(lambda i: i.commit))
+
+# Rustdoc is required by Rust tests below.
+option(env="RUSTDOC", nargs=1, help="Path to the rustdoc program")
+
+rustdoc = check_prog(
+    "RUSTDOC",
+    ["rustdoc"],
+    paths=rust_search_path,
+    input="RUSTDOC",
+    allow_missing=True,
+)
+
+# This option is separate from --enable-tests because Rust tests are particularly
+# expensive in terms of compile time (especially for code in libxul).
+option(
+    "--enable-rust-tests",
+    help="Enable building and running of Rust tests during `make check`",
+)
+
+
+@depends("--enable-rust-tests", rustdoc)
+def rust_tests(enable_rust_tests, rustdoc):
+    if enable_rust_tests and not rustdoc:
+        die("--enable-rust-tests requires rustdoc")
+    return bool(enable_rust_tests)
+
+
+set_config("MOZ_RUST_TESTS", rust_tests)
+
+
+@depends(target, c_compiler, rustc)
+@imports("os")
+def rustc_natvis_ldflags(target, compiler_info, rustc):
+    if target.kernel == "WINNT" and compiler_info.type == "clang-cl":
+        sysroot = check_cmd_output(rustc, "--print", "sysroot").strip()
+        etc = os.path.join(sysroot, "lib/rustlib/etc")
+        ldflags = []
+        if os.path.isdir(etc):
+            for f in os.listdir(etc):
+                if f.endswith(".natvis"):
+                    ldflags.append("-NATVIS:" + normsep(os.path.join(etc, f)))
+        return ldflags
+
+
+set_config("RUSTC_NATVIS_LDFLAGS", rustc_natvis_ldflags)
+
+
+option(
+    "--enable-rust-debug",
+    default=depends(when="--enable-debug")(lambda: True),
+    help="{Build|Do not build} Rust code with debug assertions turned " "on.",
+)
+
+
+@depends(when="--enable-rust-debug")
+def debug_rust():
+    return True
+
+
+set_config("MOZ_DEBUG_RUST", debug_rust)
+set_define("MOZ_DEBUG_RUST", debug_rust)
+
+# ==============================================================
+
+option(env="RUSTFLAGS", nargs=1, help="Rust compiler flags")
+set_config("RUSTFLAGS", depends("RUSTFLAGS")(lambda flags: flags))
+
+
+# Rust compiler flags
+# ==============================================================
+
+
+@depends(moz_optimize)
+def rustc_opt_level_default(moz_optimize):
+    return "2" if moz_optimize.optimize else "0"
+
+
+option(
+    env="RUSTC_OPT_LEVEL",
+    default=rustc_opt_level_default,
+    nargs=1,
+    help="Rust compiler optimization level (-C opt-level=%s)",
+)
+
+
+@depends("RUSTC_OPT_LEVEL")
+def rustc_opt_level(opt_level_option):
+    return opt_level_option[0]
+
+
+set_config("CARGO_PROFILE_RELEASE_OPT_LEVEL", rustc_opt_level)
+set_config("CARGO_PROFILE_DEV_OPT_LEVEL", rustc_opt_level)
+
+
+@depends(
+    rustc_opt_level,
+    debug_rust,
+    target,
+    "--enable-debug-symbols",
+    "--enable-frame-pointers",
+    path_remapping,
+    path_remappings,
+)
+def rust_compile_flags(
+    opt_level,
+    debug_rust,
+    target,
+    debug_symbols,
+    frame_pointers,
+    path_remapping,
+    path_remappings,
+):
+    # Cargo currently supports only two interesting profiles for building:
+    # development and release. Those map (roughly) to --enable-debug and
+    # --disable-debug in Gecko, respectively.
+    #
+    # But we'd also like to support an additional axis of control for
+    # optimization level. Since Cargo only supports 2 profiles, we're in
+    # a bit of a bind.
+    #
+    # Code here derives various compiler options given other configure options.
+    # The options defined here effectively override defaults specified in
+    # Cargo.toml files.
+
+    debug_assertions = None
+    debug_info = None
+
+    # opt-level=0 implies -C debug-assertions, which may not be desired
+    # unless Rust debugging is enabled.
+    if opt_level == "0" and not debug_rust:
+        debug_assertions = False
+
+    if debug_symbols:
+        debug_info = "2"
+
+    opts = []
+
+    if debug_assertions is not None:
+        opts.append("debug-assertions=%s" % ("yes" if debug_assertions else "no"))
+    if debug_info is not None:
+        opts.append("debuginfo=%s" % debug_info)
+    if frame_pointers:
+        opts.append("force-frame-pointers=yes")
+    # CFG for arm64 is crashy, see `def security_hardening_cflags`.
+    if target.kernel == "WINNT" and target.cpu != "aarch64":
+        opts.append("control-flow-guard=yes")
+
+    flags = []
+    for opt in opts:
+        flags.extend(["-C", opt])
+
+    if "rust" in path_remapping:
+        # rustc has supported --remap-path-prefix since version 1.26, well
+        # before our required minimum Rust version, so there's no need to
+        # feature-detect or gate on versions.
+        for old, new in path_remappings:
+            flags.append(f"--remap-path-prefix={old}={new}")
+
+    return flags
+
+
+# Rust incremental compilation
+# ==============================================================
+
+
+option("--disable-cargo-incremental", help="Disable incremental rust compilation.")
+
+
+@depends(
+    developer_options,
+    debug_rust,
+    "MOZ_AUTOMATION",
+    code_coverage,
+    "--disable-cargo-incremental",
+    using_sccache,
+    "RUSTC_WRAPPER",
+)
+@imports("os")
+def cargo_incremental(
+    developer_options,
+    debug_rust,
+    automation,
+    code_coverage,
+    enabled,
+    using_sccache,
+    rustc_wrapper,
+):
+    """Return a value for the CARGO_INCREMENTAL environment variable."""
+
+    if not enabled:
+        return "0"
+    elif enabled.origin != "default":
+        return "1"
+
+    # We never want to use incremental compilation in automation.  sccache
+    # handles our automation use case much better than incremental compilation
+    # would.
+    if automation:
+        return "0"
+
+    # Coverage instrumentation doesn't play well with incremental compilation
+    # https://github.com/rust-lang/rust/issues/50203.
+    if code_coverage:
+        return "0"
+
+    # Incremental compilation doesn't work as well as it should, and if we're
+    # using sccache, it's better to use sccache than incremental compilation.
+    if not using_sccache and rustc_wrapper:
+        rustc_wrapper = os.path.basename(rustc_wrapper[0])
+        if os.path.splitext(rustc_wrapper)[0].lower() == "sccache":
+            using_sccache = True
+    if using_sccache:
+        return "0"
+
+    # Incremental compilation is automatically turned on for debug builds, so
+    # we don't need to do anything special here.
+    if debug_rust:
+        return
+
+    # Don't enable on --enable-release builds, because of the runtime
+    # performance cost.
+    if not developer_options:
+        return
+
+    # We're clear to use incremental compilation!
+    return "1"
+
+
+set_config("CARGO_INCREMENTAL", cargo_incremental)
+
+
+@depends(rust_compile_flags, "--enable-warnings-as-errors", rustc_info)
+def rust_flags(compile_flags, warnings_as_errors, rustc_info):
+    warning_flags = []
+
+    # Note that cargo passes --cap-lints warn to rustc for third-party code, so
+    # we don't need a very complicated setup.
+    if warnings_as_errors:
+        warning_flags.append("-Dwarnings")
+        # Work around https://github.com/rust-lang/rust/issues/84428
+        if rustc_info.version >= "1.52":
+            warning_flags.append("-Aproc-macro-back-compat")
+    else:
+        warning_flags.extend(("--cap-lints", "warn"))
+
+    return compile_flags + warning_flags
+
+
+set_config("MOZ_RUST_DEFAULT_FLAGS", rust_flags)